EP0470687A2 - Magneto-resistive sensor - Google Patents
Magneto-resistive sensor Download PDFInfo
- Publication number
- EP0470687A2 EP0470687A2 EP91302259A EP91302259A EP0470687A2 EP 0470687 A2 EP0470687 A2 EP 0470687A2 EP 91302259 A EP91302259 A EP 91302259A EP 91302259 A EP91302259 A EP 91302259A EP 0470687 A2 EP0470687 A2 EP 0470687A2
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- EP
- European Patent Office
- Prior art keywords
- magneto
- resistive element
- resistive
- terminals
- active region
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/127—Structure or manufacture of heads, e.g. inductive
- G11B5/33—Structure or manufacture of flux-sensitive heads, i.e. for reproduction only; Combination of such heads with means for recording or erasing only
- G11B5/39—Structure or manufacture of flux-sensitive heads, i.e. for reproduction only; Combination of such heads with means for recording or erasing only using magneto-resistive devices or effects
- G11B5/3903—Structure or manufacture of flux-sensitive heads, i.e. for reproduction only; Combination of such heads with means for recording or erasing only using magneto-resistive devices or effects using magnetic thin film layers or their effects, the films being part of integrated structures
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
- G01R33/06—Measuring direction or magnitude of magnetic fields or magnetic flux using galvano-magnetic devices
- G01R33/09—Magnetoresistive devices
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
- G01R33/06—Measuring direction or magnitude of magnetic fields or magnetic flux using galvano-magnetic devices
- G01R33/09—Magnetoresistive devices
- G01R33/096—Magnetoresistive devices anisotropic magnetoresistance sensors
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/02—Recording, reproducing, or erasing methods; Read, write or erase circuits therefor
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/127—Structure or manufacture of heads, e.g. inductive
- G11B5/33—Structure or manufacture of flux-sensitive heads, i.e. for reproduction only; Combination of such heads with means for recording or erasing only
- G11B5/39—Structure or manufacture of flux-sensitive heads, i.e. for reproduction only; Combination of such heads with means for recording or erasing only using magneto-resistive devices or effects
- G11B5/3903—Structure or manufacture of flux-sensitive heads, i.e. for reproduction only; Combination of such heads with means for recording or erasing only using magneto-resistive devices or effects using magnetic thin film layers or their effects, the films being part of integrated structures
- G11B5/3906—Details related to the use of magnetic thin film layers or to their effects
- G11B5/3929—Disposition of magnetic thin films not used for directly coupling magnetic flux from the track to the MR film or for shielding
- G11B5/3935—Flux closure films not being part of the track flux guides
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/127—Structure or manufacture of heads, e.g. inductive
- G11B5/33—Structure or manufacture of flux-sensitive heads, i.e. for reproduction only; Combination of such heads with means for recording or erasing only
- G11B5/39—Structure or manufacture of flux-sensitive heads, i.e. for reproduction only; Combination of such heads with means for recording or erasing only using magneto-resistive devices or effects
- G11B5/3903—Structure or manufacture of flux-sensitive heads, i.e. for reproduction only; Combination of such heads with means for recording or erasing only using magneto-resistive devices or effects using magnetic thin film layers or their effects, the films being part of integrated structures
- G11B5/398—Specially shaped layers
Definitions
- This invention relates to magneto-resistive sensors.
- Magneto-resistive sensors are used in magnetic storage systems to detect magnetically encoded information.
- a changing magnetic field modulates the resistivity of the magneto-resistive sensor.
- the resulting change in resistance is detected by passing a sense current through the magneto-resistive sensor and measuring the voltage drop across the magneto-resistive sensor.
- the resulting voltage signal can be used to recover information from a magnetic storage medium such as a magnetic disk.
- Magnetic metal alloys for example, nickel iron (Ni 8 oFe 2 o).
- Ni 8 oFe 2 o nickel iron
- the nickel iron alloy is deposited in a thin film upon a substrate or wafer. Changing magnetic fields in a magnetic storage medium produce changes in the magnetisation of the magneto-resistive sensor and thereby change the resistance of the sensor.
- Detection circuitry is connected to the magneto-resistive sensor so that the changing resistance of the magneto-resistive sensor can be monitored to produce an output which is representative of information stored on the magnetic storage medium.
- the over-riding goal of all magneto-resistive sensor designs is to develop a device which is free from Barkhausen noise. This is achieved using the "hammer head” design described in US-A-4,535,375 which uses a tapped "barber pole” array.
- the barber pole array develops a longitudinal magnetic field to stabilise a central single domain region and thereby eliminate the possibility of signal degradation due to Barkhausen noise.
- This structure provides reproducible, stable magneto-resistive sensors.
- Four electrical connections are needed to operate a magneto-resistive sensor using the "hammer head” design.
- an integrated inductive write/magneto-resistive read head requires at least two additional leads for a write coil. Therefore, an integrated inductive write/magneto-resistive read head using the "hammer head” design requires a minimum of six electrical connections.
- a magneto-resistive head which requires fewer connections to the magneto-resistive element, while maintaining the single domain integrity of the sensor, would improve reliability, decrease manufacturing costs and be a significant contribution to the art of magneto-resistive heads.
- the present invention seeks to provide a magneto-resistive sensor designed to eliminate Barkhausen noise by stabilising a single domain magnetisation state in the active region of the magneto-resistive element and which uses only two electrical connections to the magneto-resistive element .
- a magneto-resistive comprising: an elongated magneto-resistive element having an active region for sensing information stored upon a magnetic storage medium and having a first wing region; first and second terminals applied to opposite ends of the magneto-resistive element; and first means connected to the magneto-resistive element for electrically shorting out AC signals generated by the first wing region of the magneto-resistive element.
- a magneto-resistive sensor preferably includes a plurality of electrically conductive strips applied to the magneto-resistive element and spaced between the first and second ends.
- the said first means may be a capacitor connected between a first conductive strip and the first terminal.
- the magneto-resistive element has a second wing region, the active region being disposed between the first and second wing regions, and by second means connected to the magneto-resistive element for electrically shorting out AC signals generated by the second wing region of the magneto-resistive element.
- Said second means may be a capacitor connected between the second conductive strip and the second terminal, the second conductive strip being further spaced from the first end of the magneto-resistive element than the first conductive strip.
- the present invention provides a magneto-resistive sensor needing only two electrical connections without sacrifice of the stability or re- produceability in the magnetic domain pattern of the magneto-resistive sensor.
- a sense current is provided to terminals on ends of the magneto-resistive sensor. Voltage sense terminals are connected to an active region of the magneto-resistive element. The voltage sense terminals are located between the end terminals. Blocking or isolation capacitors are provided between the end terminals and the voltage sense terminals which are positioned between the end terminals.
- adjacent tracks which underlie wing regions of the extended magneto-resistive sensor will not contribute a coherent noise signal to the on track signal which would render the configuration useless.
- the isolation capacitors allow the sense current to be applied throughout the entire barber pole array so that the stabilising effect of the barber pole array is not lost.
- off track performance is provided along with a highly stable design.
- isolation capacitors in accordance with the present invention, a DC sense current is applied throughout the entire length of the barber pole array. Furthermore the capacitors do not alter the longitudinal stability field generated by the barber pole array. A data signal for magnetically stored information, however, is an AC signal which is not locked by the isolation capacitors. Thus, the terminals of a magneto-resistive sensor made in accordance with the present invention, carry both the DC sense current and an AC data signal. A larger valued capacitor provides smaller attenuation to the AC data signal.
- the present invention provides the benefits of a four terminal magneto-resistive sensor design and uses only two pairs of terminals.
- the magnetic storage disk 12 includes a surface 16 divided into data tracks 18 and data sectors 20.
- the data tracks 18 extend radially around the surface 16 and the data sectors 20 extend axially from a centre of rotation 30 of the magnetic storage disk 12.
- the arm 14 includes a support arm 22 and a flexure arm 24.
- the flexure are 24 carries a slider 26 at its distal end.
- the slider 26 carries a magneto-resistive sensor (not shown in Figure 1).
- the arm 14 rotates about an axis of rotation 28 so that the slider 26 moves radially across the surface of the disk 12. As the magnetic disk 12 rotates about the axis 30, the slider 26 "flies” slightly above the surface 16. By rotating the arm 14 about the axis 28, the slider 26 moves between adjacent tracks 18 above the surface 16.
- Figure 2 is a perspective view of the flexure arm 24 and the slider 26.
- the slider 26 includes rails 32, 34 which contribute to the aero-dynamic properties of the slider.
- the slider 26 also carries magneto-resistive heads 36 (see Figure 3). Magneto-resistive heads 36 are connected to electrical conductors 38.
- Figures 3 and 4 are perspective views of the slider 26.
- the magneto-resistive heads 36 include four electrical connections, two of which are used for a write coil and two of which are used for read back of magnetically stored information.
- FIG. 5 shows a magneto-resistive sensor 40 according to the present invention.
- the magneto-resistive sensor 40 comprises a portion of magneto-resistive head 36 and includes a magneto-resistive element 42.
- the magneto-resistive sensor 40 is shown relative to a data track 18 of the surface 16.
- the magneto-resistive element 42 includes a first end 44, a second end 46 and a central active region 48.
- Equipotential strips 50, 52, 54, 56, 58, 60, 62, 64, 66 are positioned along the length of the magneto-resistive element 42.
- the strips 50 to 66 are positioned at an angle 68 with respect to the length direction of the magneto-resistive element 42.
- the magneto-resistive sensor 40 includes terminals 70, 72 and capacitors 74, 76.
- the capacitor 74 is connected to the strip 56 through an electrical conductor 78, and to the strip 50 through an electrical conductor 80.
- the capacitor 76 is connected to the strip 62 through an electrical conductor 82 and to the strip 66 through an electrical conductor 84.
- the terminals 70, 72 are connected to the strips 50, 56, respectively.
- Data sense circuitry 86 connects to the terminals 70, 72 of the magneto-resistive sensor 40.
- the data sense circuitry 86 includes a current source 88 and a voltage sensor 90.
- the current source 88 is electrically connected between the terminals 70 and electrical ground 92.
- the voltage sensor 90 is electrically connected to the terminal 70 and the terminal 72 and electrical ground 92.
- the voltage sensor 90 is connected to measure the voltage difference between the terminals 70, 72 of the magneto-resistive sensor 40.
- the current source 88 drives current through the magneto-resistive element 42 from the strip 50 towards the strip 66. This current will leave and enter each strip 50 to 66 in a direction normal to the edge of the magneto-resistive element.
- the capacitors 74, 76 block DC current from the current source 88.
- DC current enters the magneto-resistive sensor 40 through the strip 50 and exits the magneto-resistive sensor 40 through the strip 66.
- the data track 18 carries magnetically encoded information. This information sets up a magnetic field in the central active region 48 of the magneto-resistive sensor 40. As the magneto-resistive sensor 40 moves across the surface 16, the magnetic fields through the active region 48 changes. The changing magnetic field alters the resistance of the active region 48 of the magneto-resistive sensor 40, which changes the voltage drop across the active region. This causes a changing voltage drop between the strip 56 and the strip 62. The changing voltage drops sets up an AC signal between the strips 56, 62.
- the capacitors 74, 76 lock the DC sense current provided by the current source 88 but allow the AC signal from the strips 56, 62 to pass.
- the voltage sensor 90 connected between the terminals 70, 72 detects the AC signal between the strips 56, 62. This data signal is representative of magnetically encoded information recorded upon the data track 18 of the surface 16.
- the capacitors 74, 76 are manufactured directly upon a wafer which carries the magneto-resistive sensor 40.
- the electrical conductors 78 to 84 are also fabricated directly upon the wafer.
- the terminals 70, 72 provide bonding pads to allow connection to the magneto-resistive sensor 40.
- the sense current from the current source 88 is allowed to pass through the entire "barber pole" of the magneto-resistive sensor 40 to achieve maximum benefits provided by the "hammer head” design to eliminate Barkhausen noise.
- the capacitors 74, 76 reduce the active region in which magnetically encoded data is sensed, so that spurious signals picked up by the "wing" portions (the two areas on each side of the active region 48) do not contribute to the AC voltage signal sensed by the voltage sensor 90. Signals picked up by the wing portions of the magneto-resistive sensor 40 cause resistance variations between the strips 50 and 56 or the strips 60 and 66. However, any AC signal generated due to these resistance variations are electrically shorted by the capacitors 74, 76.
- Figure 6 shows another embodiment of a magneto-resistive sensor 94 according to the present invention. Like parts in Figures 5 and 6 have been designated by the same reference numerals and only the differences between the embodiments will be described in detail.
- an active region 96 of the magneto-resistive element 42 is positioned over the data track 18 of the surface 16.
- a blocking capacitor 98 is connected between the strip 50 and the strip 62. The capacitor 98 connects to the strip 50 through a conductor 100 and to the strip 62 through a conductor 102.
- the strip 66 connects to the terminal 72 through an electrical conductor 104.
- the active region 96 has been moved toward the second end 46 of the magneto-resistive element 42.
- a single blocking capacitor 98 can be used.
- the current source 88 drives a sense current through the entire length of the magneto-resistive element 42, between the strip 50 and the strip 66.
- the capacitor 98 electrically shorts any AC signals which develop between the strip 50 and the strip 62.
- the capacitor 98 allows any AC signal developed between the strip 62 and the strip 66 to pass to the terminal 70.
- the voltage sensor 90 connected between the terminal 70 and the terminal 72 detects any AC signal developed between them which carry AC signals developed between the strips 62, 66.
- the capacitor 98 prevents DC current from flowing along the conductor 102 into the strip 62.
- the capacitor 98 and electrical conductors 100, 102, 104 are preferably fabricated directly upon a wafer which carries the magneto-resistive sensor 94.
- the magneto-resistive sensor 94 shown in Figure 6 exhibits the benefit of the barber pole and only requires two terminals.
- capacitors In selecting capacitors, larger sized capacitors provide greater attenuation to the off track AC data read back signal.
- the capacitors provide a one pole filter.
- the frequency of the data signal In selecting the size of the capacitors, the frequency of the data signal must be considered. Typically 0.1 micro-Farad capacitors should be sufficient.
- the present invention provides a "hammer head” design magneto-resistive sensor which uses a barber pole element to reduce Barkhausen noise and which requires only two electrical connections to operate.
- Blocking capacitors are used to develop two different signal paths, one for the DC sense current which passes through the entire length of the barber pole element, and one for the AC data signal which originates in the active region of the magneto-resistive element.
- the blocking capacitors are fabricated directly upon the wafer which is used to carry the magneto-resistive sensor. Because only two terminals are used in magneto-resistive sensors according to the present invention, it provides magneto-resistive sensors which are easier to manufacture and offer improved reliability.
- the illustrated embodiments of the present invention are "hammer head” design magneto-resistive sensors which use barber pole magneto-resistive elements, the present invention is applicable to any magneto-resistive head design where it is desirable to reduce the number of terminals needed to operate the magneto-resistive sensor. Additionally, although capacitors have been shown, any type of filtering circuit or device may be used.
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- Physics & Mathematics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Measuring Magnetic Variables (AREA)
- Magnetic Heads (AREA)
- Hall/Mr Elements (AREA)
Abstract
Description
- This invention relates to magneto-resistive sensors.
- Magneto-resistive sensors are used in magnetic storage systems to detect magnetically encoded information. A changing magnetic field modulates the resistivity of the magneto-resistive sensor. The resulting change in resistance is detected by passing a sense current through the magneto-resistive sensor and measuring the voltage drop across the magneto-resistive sensor. The resulting voltage signal can be used to recover information from a magnetic storage medium such as a magnetic disk.
- Practical magneto-resistive sensors are typically formed using ferro-magnetic metal alloys, for example, nickel iron (Ni8oFe2o). The nickel iron alloy is deposited in a thin film upon a substrate or wafer. Changing magnetic fields in a magnetic storage medium produce changes in the magnetisation of the magneto-resistive sensor and thereby change the resistance of the sensor.
- As many as four electrical connections to the magneto-resistive sensor are needed to use the head read back stored information. Two connections are used to supply electrical current through the sensor, and two other connections are used to detect changes in voltage across an active region of the head due to the change in resistance associated with the presence of a magnetic field near the magneto-resistive sensor. Detection circuitry is connected to the magneto-resistive sensor so that the changing resistance of the magneto-resistive sensor can be monitored to produce an output which is representative of information stored on the magnetic storage medium.
- The over-riding goal of all magneto-resistive sensor designs is to develop a device which is free from Barkhausen noise. This is achieved using the "hammer head" design described in US-A-4,535,375 which uses a tapped "barber pole" array.
- The barber pole array develops a longitudinal magnetic field to stabilise a central single domain region and thereby eliminate the possibility of signal degradation due to Barkhausen noise. This structure provides reproducible, stable magneto-resistive sensors. Four electrical connections are needed to operate a magneto-resistive sensor using the "hammer head" design. Additionally, an integrated inductive write/magneto-resistive read head requires at least two additional leads for a write coil. Therefore, an integrated inductive write/magneto-resistive read head using the "hammer head" design requires a minimum of six electrical connections.
- A magneto-resistive head which requires fewer connections to the magneto-resistive element, while maintaining the single domain integrity of the sensor, would improve reliability, decrease manufacturing costs and be a significant contribution to the art of magneto-resistive heads.
- The present invention seeks to provide a magneto-resistive sensor designed to eliminate Barkhausen noise by stabilising a single domain magnetisation state in the active region of the magneto-resistive element and which uses only two electrical connections to the magneto-resistive element .
- According to the present invention there is provided a magneto-resistive comprising: an elongated magneto-resistive element having an active region for sensing information stored upon a magnetic storage medium and having a first wing region; first and second terminals applied to opposite ends of the magneto-resistive element; and first means connected to the magneto-resistive element for electrically shorting out AC signals generated by the first wing region of the magneto-resistive element.
- A magneto-resistive sensor preferably includes a plurality of electrically conductive strips applied to the magneto-resistive element and spaced between the first and second ends.
- The said first means may be a capacitor connected between a first conductive strip and the first terminal.
- In one embodiment the magneto-resistive element has a second wing region, the active region being disposed between the first and second wing regions, and by second means connected to the magneto-resistive element for electrically shorting out AC signals generated by the second wing region of the magneto-resistive element. Said second means may be a capacitor connected between the second conductive strip and the second terminal, the second conductive strip being further spaced from the first end of the magneto-resistive element than the first conductive strip.
- The present invention provides a magneto-resistive sensor needing only two electrical connections without sacrifice of the stability or re- produceability in the magnetic domain pattern of the magneto-resistive sensor. In the present invention, a sense current is provided to terminals on ends of the magneto-resistive sensor. Voltage sense terminals are connected to an active region of the magneto-resistive element. The voltage sense terminals are located between the end terminals. Blocking or isolation capacitors are provided between the end terminals and the voltage sense terminals which are positioned between the end terminals. In the present invention, adjacent tracks which underlie wing regions of the extended magneto-resistive sensor will not contribute a coherent noise signal to the on track signal which would render the configuration useless. The isolation capacitors allow the sense current to be applied throughout the entire barber pole array so that the stabilising effect of the barber pole array is not lost. In the present invention, off track performance is provided along with a highly stable design.
- Using isolation capacitors in accordance with the present invention, a DC sense current is applied throughout the entire length of the barber pole array. Furthermore the capacitors do not alter the longitudinal stability field generated by the barber pole array. A data signal for magnetically stored information, however, is an AC signal which is not locked by the isolation capacitors. Thus, the terminals of a magneto-resistive sensor made in accordance with the present invention, carry both the DC sense current and an AC data signal. A larger valued capacitor provides smaller attenuation to the AC data signal. The present invention provides the benefits of a four terminal magneto-resistive sensor design and uses only two pairs of terminals.
- The invention is illustrated, merely by way of example, in the accompanying drawings, in which:-
- Figure 1 is a top plan view of a support arm and a magnetic storage disk;
- Figure 2 is a perspective view of a flexure arm and slider;
- Figure 3 is a perspective view of the slider of Figure 2;
- Figure 4 is a perspective view of magneto-resistive heads mounted on the slider of Figure 3;
- Figure 5 shows a first embodiment of a magneto-resistive sensor according to the present invention; and
- Figure 6 shows a second embodiment of a magneto-resistive sensor according to the present invention.
- Figure 1 is a top plan view of a
magnetic storage system 10 including amagnetic storage disk 12 and an arm 14. - The
magnetic storage disk 12 includes asurface 16 divided intodata tracks 18 anddata sectors 20. Thedata tracks 18 extend radially around thesurface 16 and thedata sectors 20 extend axially from a centre ofrotation 30 of themagnetic storage disk 12. - The arm 14 includes a
support arm 22 and aflexure arm 24. The flexure are 24 carries aslider 26 at its distal end. Theslider 26 carries a magneto-resistive sensor (not shown in Figure 1). - The arm 14 rotates about an axis of
rotation 28 so that theslider 26 moves radially across the surface of thedisk 12. As themagnetic disk 12 rotates about theaxis 30, theslider 26 "flies" slightly above thesurface 16. By rotating the arm 14 about theaxis 28, theslider 26 moves betweenadjacent tracks 18 above thesurface 16. - Figure 2 is a perspective view of the
flexure arm 24 and theslider 26. Theslider 26 includesrails slider 26 also carries magneto-resistive heads 36 (see Figure 3). Magneto-resistive heads 36 are connected toelectrical conductors 38. - Figures 3 and 4 are perspective views of the
slider 26. The magneto-resistive heads 36 include four electrical connections, two of which are used for a write coil and two of which are used for read back of magnetically stored information. - Figure 5 shows a magneto-resistive sensor 40 according to the present invention. The magneto-resistive sensor 40 comprises a portion of magneto-
resistive head 36 and includes a magneto-resistive element 42. The magneto-resistive sensor 40 is shown relative to adata track 18 of thesurface 16. The magneto-resistive element 42 includes afirst end 44, asecond end 46 and a centralactive region 48. Equipotential strips 50, 52, 54, 56, 58, 60, 62, 64, 66 are positioned along the length of the magneto-resistive element 42. Thestrips 50 to 66 are positioned at anangle 68 with respect to the length direction of the magneto-resistive element 42. The magneto-resistive sensor 40 includesterminals capacitors capacitor 74 is connected to thestrip 56 through anelectrical conductor 78, and to thestrip 50 through anelectrical conductor 80. Thecapacitor 76 is connected to thestrip 62 through anelectrical conductor 82 and to thestrip 66 through anelectrical conductor 84. Theterminals strips -
Data sense circuitry 86 connects to theterminals circuitry 86 includes acurrent source 88 and avoltage sensor 90. Thecurrent source 88 is electrically connected between theterminals 70 andelectrical ground 92. Thevoltage sensor 90 is electrically connected to the terminal 70 and the terminal 72 andelectrical ground 92. Thevoltage sensor 90 is connected to measure the voltage difference between theterminals - The
current source 88 drives current through the magneto-resistive element 42 from thestrip 50 towards thestrip 66. This current will leave and enter eachstrip 50 to 66 in a direction normal to the edge of the magneto-resistive element. - The
capacitors current source 88. Thus, DC current enters the magneto-resistive sensor 40 through thestrip 50 and exits the magneto-resistive sensor 40 through thestrip 66. The data track 18 carries magnetically encoded information. This information sets up a magnetic field in the centralactive region 48 of the magneto-resistive sensor 40. As the magneto-resistive sensor 40 moves across thesurface 16, the magnetic fields through theactive region 48 changes. The changing magnetic field alters the resistance of theactive region 48 of the magneto-resistive sensor 40, which changes the voltage drop across the active region. This causes a changing voltage drop between thestrip 56 and thestrip 62. The changing voltage drops sets up an AC signal between thestrips capacitors current source 88 but allow the AC signal from thestrips voltage sensor 90 connected between theterminals strips data track 18 of thesurface 16. - In the preferred embodiment of the present invention shown in Figure 5, the
capacitors electrical conductors 78 to 84 are also fabricated directly upon the wafer. Theterminals current source 88 is allowed to pass through the entire "barber pole" of the magneto-resistive sensor 40 to achieve maximum benefits provided by the "hammer head" design to eliminate Barkhausen noise. Thecapacitors voltage sensor 90. Signals picked up by the wing portions of the magneto-resistive sensor 40 cause resistance variations between thestrips strips 60 and 66. However, any AC signal generated due to these resistance variations are electrically shorted by thecapacitors - Figure 6 shows another embodiment of a magneto-resistive sensor 94 according to the present invention. Like parts in Figures 5 and 6 have been designated by the same reference numerals and only the differences between the embodiments will be described in detail. In Figure 6, an
active region 96 of the magneto-resistive element 42 is positioned over thedata track 18 of thesurface 16. A blockingcapacitor 98 is connected between thestrip 50 and thestrip 62. Thecapacitor 98 connects to thestrip 50 through aconductor 100 and to thestrip 62 through aconductor 102. Thestrip 66 connects to the terminal 72 through anelectrical conductor 104. - In the magneto-resistive sensor 94, the
active region 96 has been moved toward thesecond end 46 of the magneto-resistive element 42. Using this configuration, asingle blocking capacitor 98 can be used. Thecurrent source 88 drives a sense current through the entire length of the magneto-resistive element 42, between thestrip 50 and thestrip 66. Thecapacitor 98 electrically shorts any AC signals which develop between thestrip 50 and thestrip 62. However, thecapacitor 98 allows any AC signal developed between thestrip 62 and thestrip 66 to pass to the terminal 70. Thevoltage sensor 90, connected between the terminal 70 and the terminal 72 detects any AC signal developed between them which carry AC signals developed between thestrips capacitor 98 prevents DC current from flowing along theconductor 102 into thestrip 62. - The
capacitor 98 andelectrical conductors - In selecting capacitors, larger sized capacitors provide greater attenuation to the off track AC data read back signal. The capacitors provide a one pole filter. In selecting the size of the capacitors, the frequency of the data signal must be considered. Typically 0.1 micro-Farad capacitors should be sufficient.
- The present invention provides a "hammer head" design magneto-resistive sensor which uses a barber pole element to reduce Barkhausen noise and which requires only two electrical connections to operate. Blocking capacitors are used to develop two different signal paths, one for the DC sense current which passes through the entire length of the barber pole element, and one for the AC data signal which originates in the active region of the magneto-resistive element. The blocking capacitors are fabricated directly upon the wafer which is used to carry the magneto-resistive sensor. Because only two terminals are used in magneto-resistive sensors according to the present invention, it provides magneto-resistive sensors which are easier to manufacture and offer improved reliability.
- Although the illustrated embodiments of the present invention are "hammer head" design magneto-resistive sensors which use barber pole magneto-resistive elements, the present invention is applicable to any magneto-resistive head design where it is desirable to reduce the number of terminals needed to operate the magneto-resistive sensor. Additionally, although capacitors have been shown, any type of filtering circuit or device may be used.
Claims (9)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US563990 | 1990-08-07 | ||
US07/563,990 US5065094A (en) | 1990-08-07 | 1990-08-07 | Two terminal magnetoresistive sensor having DC blocking capacitor |
Publications (3)
Publication Number | Publication Date |
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EP0470687A2 true EP0470687A2 (en) | 1992-02-12 |
EP0470687A3 EP0470687A3 (en) | 1993-10-13 |
EP0470687B1 EP0470687B1 (en) | 1998-05-06 |
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Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP91302259A Expired - Lifetime EP0470687B1 (en) | 1990-08-07 | 1991-03-15 | Magneto-resistive sensor |
Country Status (7)
Country | Link |
---|---|
US (1) | US5065094A (en) |
EP (1) | EP0470687B1 (en) |
JP (1) | JP2693276B2 (en) |
DE (1) | DE69129347T2 (en) |
HK (1) | HK1009356A1 (en) |
MY (1) | MY106391A (en) |
SG (1) | SG47740A1 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6586012B2 (en) | 1999-07-09 | 2003-07-01 | Ortho-Mcneil Pharmaceutical, Inc. | Taste masked pharmaceutical liquid formulations |
Families Citing this family (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0478256B1 (en) * | 1990-09-27 | 1997-05-14 | Kabushiki Kaisha Toshiba | Magnetic head |
US5420736A (en) * | 1994-04-15 | 1995-05-30 | International Business Machines Corporation | MR read transducer with thermal noise cancellation |
US5696445A (en) * | 1994-09-26 | 1997-12-09 | Phase Metrics | Method and apparatus for testing the resistive properties of magneto resistive materials using a time variable magnetic field |
US5587857A (en) * | 1994-10-18 | 1996-12-24 | International Business Machines Corporation | Silicon chip with an integrated magnetoresistive head mounted on a slider |
JPH0991623A (en) * | 1995-09-19 | 1997-04-04 | Hitachi Ltd | Magneto-resistive head and its production |
US5654854A (en) * | 1995-11-30 | 1997-08-05 | Quantum Corporation | Longitudinally biased magnetoresistive sensor having a concave shaped active region to reduce Barkhausen noise by achieving a substantially single magnetic domain state |
JP2000099924A (en) * | 1998-09-18 | 2000-04-07 | Nippon Hoso Kyokai <Nhk> | Magnetic reproducing head |
CN100346492C (en) * | 2005-05-20 | 2007-10-31 | 中国科学院合肥物质科学研究院 | Magnetosensitive sensor array and manufacturing method thereof |
US9159344B2 (en) | 2013-05-08 | 2015-10-13 | Western Digital Technologies, Inc. | Disk drive read circuit comprising an AC coupled sense amplifier for amplifying a read signal |
US9047917B1 (en) | 2013-11-26 | 2015-06-02 | Western Digital Technologies, Inc. | Disk drive slider with sense amplifier for coupling to a preamp through a supply/bias line and a read signal line |
Citations (5)
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FR2308159A1 (en) * | 1975-04-15 | 1976-11-12 | Philips Nv | MAGNETIC HEAD INCLUDING A MAGNETORESISTANCE ELEMENT |
EP0037966A1 (en) * | 1980-04-15 | 1981-10-21 | Siemens Aktiengesellschaft | Magnetoresistive sensor |
JPS59185005A (en) * | 1983-04-02 | 1984-10-20 | Hitachi Ltd | Multi-channel reproducing circuit |
US4535375A (en) * | 1983-01-14 | 1985-08-13 | Magnetic Peripherals, Inc. | Magnetoresistive head |
EP0215270A1 (en) * | 1985-08-20 | 1987-03-25 | International Business Machines Corporation | Method and apparatus for reading recorded data by a magnetoresistive head |
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US3370227A (en) * | 1966-09-20 | 1968-02-20 | Gen Cable Corp | Apparatus to measure continuously corona inception and extinction voltages in movinginsulated cable cores |
US4052748A (en) * | 1974-04-01 | 1977-10-04 | U.S. Philips Corporation | Magnetoresistive magnetic head |
CA1076252A (en) * | 1975-04-14 | 1980-04-22 | Frederik W. Gorter | Magnetoresistive head |
US4190871A (en) * | 1975-06-13 | 1980-02-26 | U.S. Philips Corporation | Magnetic converter having a magnetoresistive element |
JPS5468266A (en) * | 1977-11-09 | 1979-06-01 | Nec Corp | Detector of rotating angle and number of revolutions |
NL7806568A (en) * | 1978-06-19 | 1979-12-21 | Philips Nv | MAGNETO RESISTANCE READ HEAD. |
US4255708A (en) * | 1978-12-15 | 1981-03-10 | International Business Machines Corporation | Magnetoresistive position transducer with invariable peak signal |
JPS56101617A (en) * | 1980-01-18 | 1981-08-14 | Olympus Optical Co Ltd | Multichannel magnetic head and its manufacture |
EP0053343A1 (en) * | 1980-11-28 | 1982-06-09 | Hitachi, Ltd. | Reproducing and amplifying circuit for magnetoresistive head |
JPS5845619A (en) * | 1981-09-09 | 1983-03-16 | Hitachi Ltd | Magneto-resistance effect type thin film magnetic head |
DE3279790D1 (en) * | 1981-12-09 | 1989-08-03 | Matsushita Electric Ind Co Ltd | Thin film magnetic head |
CA1209260A (en) * | 1982-10-29 | 1986-08-05 | Tetsuo Sekiya | Magnetic transducer head using magnetroresistance effect |
US4566050A (en) * | 1982-12-30 | 1986-01-21 | International Business Machines Corp. (Ibm) | Skew insensitive magnetic read head |
US4580175A (en) * | 1983-01-14 | 1986-04-01 | Magnetic Peripherals, Inc. | Endless, folded magnetoresistive head |
JPH06105481B2 (en) * | 1983-07-27 | 1994-12-21 | 株式会社東芝 | Magnetic recording / reproducing device |
DE3435867A1 (en) * | 1984-09-29 | 1986-04-10 | Bosch Gmbh Robert | DIFFERENTIAL SENSOR |
US4843506A (en) * | 1986-09-29 | 1989-06-27 | Hewlett-Packard Company | Shields of magnetoresistive transducers |
US4841398A (en) * | 1987-02-17 | 1989-06-20 | Magnetic Peripherals Inc. | Non linear magnetoresistive sensor |
US4821133A (en) * | 1987-02-17 | 1989-04-11 | Magnetic Peripherals, Inc. | Bottleneck magnetoresistive element |
JPH01184709A (en) * | 1988-01-20 | 1989-07-24 | Toshiba Corp | Thin film magnetic head |
-
1990
- 1990-08-07 US US07/563,990 patent/US5065094A/en not_active Expired - Lifetime
-
1991
- 1991-02-13 JP JP3020040A patent/JP2693276B2/en not_active Expired - Fee Related
- 1991-03-15 SG SG1996004126A patent/SG47740A1/en unknown
- 1991-03-15 DE DE69129347T patent/DE69129347T2/en not_active Expired - Fee Related
- 1991-03-15 EP EP91302259A patent/EP0470687B1/en not_active Expired - Lifetime
- 1991-03-20 MY MYPI91000463A patent/MY106391A/en unknown
-
1998
- 1998-08-19 HK HK98109999A patent/HK1009356A1/en not_active IP Right Cessation
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2308159A1 (en) * | 1975-04-15 | 1976-11-12 | Philips Nv | MAGNETIC HEAD INCLUDING A MAGNETORESISTANCE ELEMENT |
EP0037966A1 (en) * | 1980-04-15 | 1981-10-21 | Siemens Aktiengesellschaft | Magnetoresistive sensor |
US4535375A (en) * | 1983-01-14 | 1985-08-13 | Magnetic Peripherals, Inc. | Magnetoresistive head |
JPS59185005A (en) * | 1983-04-02 | 1984-10-20 | Hitachi Ltd | Multi-channel reproducing circuit |
EP0215270A1 (en) * | 1985-08-20 | 1987-03-25 | International Business Machines Corporation | Method and apparatus for reading recorded data by a magnetoresistive head |
Non-Patent Citations (1)
Title |
---|
PATENT ABSTRACTS OF JAPAN vol. 9, no. 48 (P-338)(1771) 28 February 1985 & JP-A-59 185 005 ( HITACHI SEISAKUSHO K.K. ) 20 October 1984 * |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6586012B2 (en) | 1999-07-09 | 2003-07-01 | Ortho-Mcneil Pharmaceutical, Inc. | Taste masked pharmaceutical liquid formulations |
Also Published As
Publication number | Publication date |
---|---|
DE69129347T2 (en) | 1998-09-03 |
SG47740A1 (en) | 1998-04-17 |
JPH06124422A (en) | 1994-05-06 |
MY106391A (en) | 1995-05-30 |
EP0470687A3 (en) | 1993-10-13 |
EP0470687B1 (en) | 1998-05-06 |
DE69129347D1 (en) | 1998-06-10 |
HK1009356A1 (en) | 1999-05-28 |
JP2693276B2 (en) | 1997-12-24 |
US5065094A (en) | 1991-11-12 |
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